Burgeoning Jelly

Amorphous. The jelly can move through a space as narrow as 1 inch wide without squeezing. The jelly can occupy the spaces of other creatures and vice versa. Creatures within the jelly's space take an additional 3 (1d6) acid damage at the start of each of their turns.

Regeneration. The jelly regains 10 hit points at the start of its turn. If the jelly takes fire damage, this trait doesn't function at the start of the jelly's next turn. New jellies begin one size smaller than the parent jelly, but then grow as they regain hit points. At 20 they are small, 30 medium, 40 large, 60 huge, 90+ gargantuan. The jelly's regeneration can extend its hit point maximum 5 points per round if it has full health. This goes to a maximum of 200 hit points.

Spider Climb. The jelly can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Multiattack. The jelly makes three pseudopod attacks. 

Pseudopod. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) bludgeoning damage plus 3 (1d6) acid damage.

Split. When a jelly that is Medium or larger is subjected to lightning or slashing damage, it splits into two new jellies if it has at least 10 hit points. Each new jelly has hit points equal to half the original jelly's, rounded down. New jellies are one size smaller than the original jelly.